Parallelogram P Q S R is shown. The length of P Q is (4 x minus 1) centimeters and the length of R S is (3 x + 7) centimeters.
The perimeter of parallelogram PQSR is 74 cm. What is QS?

4 cm
6 cm
8 cm
12 cm

The 6 cm

This is because sides PQ and RS are equal so set the two expressions equal

4x-1=3x+7

X=8

Then plug eight back into one of the expressions

4(8)-1=31

That means both sides PQ and RS are 31 cm, 62 cm are accounted for out of 72. Subtract 62 from 72 to find out how much is left

72-62=12

There are two sides left so divide by 2

12/2=6